A Novel Frequency Tuning and Calibration Scheme in an E-band PLL

With the rapid development of millimeter-wave communication, there is substantial research significance in the advancement of high-performance millimeter-wave phase-locked loops (PLL). This paper introduces novel components integrated into an E-band PLL, encompassing a digital controlled artificial dielectric (DiCAD) differential transmission line, a binary-to-thermometer encoder, and a digital automatic frequency calibration loop (AFC). The DiCAD in the proposed voltage-controlled oscillator (VCO) functions as a digital frequency tuning element, replacing the conventional switched capacitor array (SCA). This addresses challenges such as low quality-factor, inaccurate simulation accuracy of SCA and substantial VCO gain variation. The closed-loop AFC is designed to generate a 5-bit binary control word, subsequently converted into a 31-bit thermometer code through the encoder. Manipulating the 5-bit control word enables changes in the capacitance of the DiCAD and the frequency of the VCO output signal. Moreover, the gain of the VCO is effectively reduced by using 31-bit DiCAD transmission line. The circuit has been implemented in a standard 40nm CMOS process, with the core area of AFC module is 28µm × 28µm.